Hard impact resistant composite

ABSTRACT

A shaped article, at least one domain of which has a three-dimensionally reinforced composite structure comprising of a matrix and a reinforcing system ( 2, 4, 5, 6 ), the reinforcing system comprising bodies such as bars, wires, cables, or plates embedded in the matrix and extending three-dimensionally in first ( 4, 5 ) second ( 2 ) and third ( 6 ) dimensions therein, the reinforcing system being tension interlocked in at least one dimension in that reinforcement components extending in the first and/or second dimension are tension interlocked to reinforcement components extending in the same dimension(s), but at a transverse distance therefrom, by transverse reinforcement components extending in a dimension transverse, to a plane or surface defined by the reinforcement in the first and/or second dimension. The matrix is preferably a dense cement-based matrix prepared from cement, microsilica, a concrete superplaticiser and water, or a metallic matrix. The shaped articles are capable of absorbing high energy with retention of a substantial degree of internal coherence, e.g. under exposure to high velocity impact.

FIELD OF THE INVENTION

The present invention relates to a shaped article which is capable ofresisting impact, including high velocity impact and other high energyimpact.

A number of impact challenges, such as attacks with projectiles, shells,grenades, missiles and bombs, have as their main purpose to penetrateand/or damage the objects which they are aimed at. Another class ofpotentially damaging impact is accidental events such as gas explosions,vehicle (ships, aeroplanes, cars, etc.) collision, impact occurringduring earthquakes, and the accidental dropping of articles, e.g. in theoffshore industry.

Another type of impact is impact processing, such as impact hammering,explosion shaping, etc. Another type of impact occurs in connection withquarrying of stone. For example, large pieces of stone may fall ontotrucks or other machinery, and high energy impacts of this type cancause extensive damage.

Impact challenges also occur in the form of high energy impact from e.g.explosives. For example, bank vaults must be able to withstand anexplosive impact of this type.

In high velocity or high energy impact, the behaviour of materials is inmany ways fundamentally different from the behaviour under slow staticinfluences—often resulting, inter alia, in fatal failure or destructionof the articles in question, even where the articles have very high loadbearing capacity under static conditions.

For protection against damaging impact and for tools used for impactingprocessing, articles having better resistance against impact thanhitherto obtainable are desired.

The present invention provides such articles. The articles of theinvention can be designed to provide protection or resistance underinfluences where known art materials would fail or would be vastlyinferior, in particular high energy impact such as high velocity impact.

DISCUSSION OF THE PRIOR ART

It is known to produce various high-strength composite materials, forexample construction materials based e.g. on a matrix of Portland cementand very small particles such as ultrafine silica, and withreinforcement incorporated therein in the form of e.g. fibres, steelbars or wires, etc.

EP 010777 discloses very strong and dense composite cement-basedcomposite materials prepared from Portland cement, inorganic solidsilica dust particles, fibres, a concrete superplasticizer and water,the composite materials having a large content of silica dust particlesand superplasticizer and a small water content, e.g. typically 10-30% byvolume of silica dust particles based on the volume of the cement andsilica dust, 1-4% by weight of superplasticizer dry matter based on theweight of the cement and silica dust, and a water/powder weight ratio of0.12-0.30 based on the weight of the cement, silica dust and possibleother fine powder present.

EP 042935 discloses improved composite materials based on the matrix ofEP 010777 and additionally containing a strong aggregate with a strengthexceeding that of ordinary sand or stone used as aggregate for ordinaryconcrete.

WO 87/07597 discloses a compact reinforced composite (CRC) materialbased on a combination of a rigid, dense and strong matrix comprising abase matrix corresponding to the composite materials described in EP010777 and EP 042935 which is reinforced with a high content ofrelatively fine fibres and which is further reinforced with a highcontent of main reinforcement, e.g. in the form of steel bars, wires orcables, to result in a novel composite material which is both strong andrigid as well as ductile.

A technical paper (“Role of shear reinforcement in large-deflectionbehavior”, Kiger et al., ACI Structural Journal, November-December 1989)describes the use of “lacing” or “single-leg stirrups” in order to tiethe two principal reinforcement mats together in reinforced concretestructures designed for blast-resistance. The paper concludes thatrequirements for shear reinforcement such as lacing may be morerestrictive and expensive than necessary, and it is stated that althoughtransverse shear reinforcement (in the form of lacing or stirrups) canprovide additional confinement for reinforced concrete beams, itprovides very little, if any, additional confinement for slabs. It isfurthermore suggested that the use of smaller but more numerousprincipal reinforcing bars may be a more effective way of preventingbreakup of a concrete slab than the use of such transverse shearreinforcement. The emphasis of the paper is on the reinforcement itself,and there is no suggestion to use e.g. lacing with any particular typeof concrete matrix.

Although the principle of “lacing” of reinforcing bars in a concretestructure designed for blast-resistance, e.g. as described in thetechnical paper referred to above, was known, the prior art contains nosuggestion to combine this or a similar principle of reinforcementtogether with any particular type of concrete matrix. On the contrary,the cited technical paper suggests that an increased amount of mainreinforcing bars might be a more effective solution to the problem ofblast-resistance than the use of transverse reinforcement such aslacing. Thus, the problem of providing structures, in particularcement-based structures, with improved blast- or impact-resistanceremains unsolved.

The CRC concept described in the above-cited WO 87/07597, on the otherhand, emphasises both the nature of the matrix (a rigid, dense andstrong cement-based matrix) and the reinforcement (a high content ofreinforcing fibres together with a high content of main reinforcement inthe form of e.g. steel bars, wires or cables). However, the concept of a3-dimensional arrangement of main reinforcement, wherein individualreinforcing elements are interlocked with each other in at least onedimension, is in no way suggested by WO 87/07597, for the simple reasonthat such an intricate arrangement of reinforcement would have beenregarded by a person skilled in the art as involving an unnecessaryexpense and difficulty without any expectation of technical benefit.

BRIEF DISCUSSION OF THE INVENTION

It is an object of the present invention to provide novel shapedarticles with improved performance characteristics, in particular underdynamic conditions. One aspect of the present invention represents afurther development of the CRC concept mentioned above, enabling theproduction of materials that are extremely strong and durable under bothstatic and dynamic conditions, and which also show extremely high impactresistance.

The present invention relates in general to impact-resistant articleswhich are based on a combination of a hard, but fracture-ductile matrixand a three-dimensional reinforcement which is internally tensioninterlocked in at least one dimension. Articles according to theinvention are unique in showing high strength, rigidity and ductility inall three directions and showing, upon being subjected to a large load,high strength, toughness and rigidity, as well as the capability ofabsorbing high energy with retention of a substantial degree of internalcoherence, also under exposure to high-velocity or high-energy impact.

In its broadest aspect, the invention can be characterized as a shapedarticle, at least one domain of which has a three-dimensionallyreinforced composite structure, the composite structure comprising amatrix and a reinforcing system, the reinforcing system comprising aplurality of bodies embedded in the matrix and extendingthree-dimensionally in first, second and third dimensions therein, thereinforcing system being tension interlocked in at least one dimensionin that reinforcement components extending in the first and/or seconddimension are tension interlocked to reinforcement components extendingin the same dimension(s), but at a transverse distance therefrom, bytransverse reinforcement components extending in a dimension transverseto a plane or surface defined by the reinforcement in the first and/orsecond dimension,

the matrix having a compressive strength of at least 80 MPa, a modulusof elasticity of at least 40 GPa, and a fracture energy of at least 0.5kN/m,

the reinforcing bodies having a tensile strength of at least 200 MPa,preferably at least 400 Mpa.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, the present invention relates in particular toshaped articles that exhibit improved performance under dynamicconditions. Therefore, in a preferred embodiment of the shaped articlesof the invention, the volume proportion of the reinforcing bodies in thereinforced composite structure is at least 2%, the volume proportion inany specific direction being at least 0.5%. Preferably, the volumeproportion of the reinforcing bodies is at least 4% and the volumeproportion in any specific direction is at least 0.75%, and morepreferably the volume proportion of the reinforcing bodies is at least6% and the volume proportion in any specific direction is at least 1%.

The number of reinforcing components in the reinforced compositestructure domain will typically be at least 3, preferably at least 5, inany of the first, second and third dimensions of an arbitraryrectangular reference coordinate system in the reinforced 5 compositedomain.

It is also preferred that the ultimate strain of the reinforcing bodiesis at least 2%. However, when the reinforcing bodies have a tensilestrength between 200 and 300 MPa then the ultimate strain 10 should beat least 20%, and when the reinforcing bodies have a tensile strengthbetween 301 and 400 MPa, then the ultimate strain should be at least15%.

The reinforcement systems in the articles according to the invention maybe configured in many different ways, such as will be explained in thefollowing, but characteristic to them all is a three-dimensional grid,network or lattice of reinforcement (which may have many differentconfigurations as explained in the following) in which matrix materialas a “continuous phase” is dispersed in the interstices of the“lattice”, which also normally and preferably constitutes “a continuousphase”. Characteristic to the present invention is the fact that thereinforcement system comprises components which extend in all threedimensions, and that the concentration of reinforcement in anyparticular direction is above the above-stated minimum value.

It is also an essential feature of the invention that in at least onedirection, the reinforcement system is internally “tension interlocked”,which means that at least in that direction, the reinforcement systemcounteracts separation in that direction. The term “tension interlocked”does not necessarily mean that the reinforcement in question is undertension under static conditions, but rather that when the material isexposed to tension forces that tend to separate the interlockedcomponents of the reinforcement in question from each other, the tensioninterlocking provided by the transverse reinforcement components resiststhe separation, even under conditions of heavy destruction where matrixmight fail. This is explained in greater detail in connection with thedrawings.

This feature plays an essential role in the high velocity impactresistance achieved by the present invention: Take as an example (withreference to FIG. 11, which is discussed in greater detail below) alarge 20 cm thick panel or plate with 20% by volume of reinforcement inthe plane of the panel consisting of five layers of heavy steel barsarranged perpendicular to each other and interconnected by means of 3.1%by volume of transverse reinforcement fixing each individual steel barin the top layer with a corresponding individual steel bar in the bottomlayer. This reinforcement is embedded in and tightly fixed to a strong,stiff and fracture-ductile cement-based matrix. Such panels stopped a 47kg armour-piercing shell (diameter 152 mm) travelling at 482 m/sec, theshell ending tightly fixed in the panels with 8 cm of its rear stillextending from the front of the plate!—and with very little damage ofthe panel except in the immediate vicinity of the shell and fine mapcracking of the plate surface. In the same series of experiments, platesof the same size of high quality cement-based composite and subjected tothe same load were completely crushed into small pieces. In similarexperiments, strong plates with matrix materials substantially identicalto the above materials and strongly reinforced with reinforcementidentical to the above reinforcement, but without the essentialtransverse reinforcement, large damage occurred. The two front plates(thickness of each plate 20 cm) were completely shattered, withmaterials including 20 mm steel bars 60 meters being flung backwards bythe reflected wave. Such a large destruction is completely avoided withthe articles of the invention.

It will be understood that the shaped article does not necessarily havethe reinforced composite structure throughout the article, but that oneor several domains which fulfil the criteria stated above may be presenttogether with domains which do not conform to the criteria. As anexample may be mentioned a bank vault where a domain having the definedreinforced composite structure is hidden within a wall which has adifferent exterior.

The reinforcing system (the “main reinforcement”) will typically be madefrom bars, e.g. several layers of bars, with bars within a layer beingarranged parallel to each other, the direction of the bars in one layertypically being perpendicular to the bars in the adjacent layer orlayers. It is also possible to have layers of the reinforcementconsisting of perforated plates, possibly with other layers being, e.g.,bars or rods. The transverse components may be bars or rods bent aroundthe outer layers of the main reinforcement, or other configurations,such as illustrated in the drawings. It is also possible for thetransverse components to be integrated parts of one reinforcement body,e.g. where the reinforcement body consists of several perforated platesat a (transverse) distance from each other joined together withtransverse rods welded to the plates in such a manner that they give astrong tension interlocking.

It should be noted that several “reinforcing components” in a givendimension may be a part of a single reinforcing body. Thus, a referenceherein to a number of reinforcing components in a given dimension neednot be equivalent to the same number of independent (i.e. non-connected)reinforcing bodies. See e.g. FIG. 10 and the accompanying descriptionbelow for an illustration of this principle.

In the preferred embodiments, the transverse reinforcement componentstension interlock reinforcement components of opposite outermost planesor surfaces of the reinforcement, so that the reinforcement system as awhole resists separation in the transverse direction.

As indicated above, the reinforcing system may be tension interlocked inmore than one dimension. This may be done according to the sameprinciples described above, using e.g. rods bent around rodsperpendicular thereto, or wires/cables. Another interesting possibilityis to have adjacent longitudinal rods combined in a hairpin-likeconfiguration around and enclosing the outer layers of rodsperpendicular thereto. While this is not tension interlocking proper, itis an interesting further enhancement of the reinforcing system where atransverse tension interlocking is already present.

The matrix material is relatively strong, stiff and resistant tofracturing, such as appears from the above minimum criteria. Preferably,the matrix material has a compressive strength of at least 100 MPa,preferably at least 150 MPa, more preferably at least 200 MPa, morepreferably at least 250 MPa and most preferably at least 300 MPa. Themodulus of elasticity of the matrix material is preferably at least 60GPa, more preferably at least 80 GPa, and still more preferably at least100 GPa. The fracture energy of the matrix material is in particular atleast 1 kN/m, preferably at least 2 kN/m, more preferably at least 5kN/m, more preferably at least 10 kN/m, more preferably at least 20kN/m, and more preferably at least 30 kN/m.

As appears from the above, the reinforcing bodies combined with thestrong, stiff and fracture-resistant matrix are characterized by acombination of a high tensile strength and sufficiently high ultimatestrain, and are present in a high volume in the matrix in any particulardirection of the matrix, which means that in any cross section layer inany direction taken within the matrix domain, the volume concentrationfulfils the criteria stated. It is most advantageous that the strengthand strain parameters are higher than the minimum stated above. Thus, itis preferred that the reinforcing bodies have a tensile strength of atleast 700 MPa, preferably at least 1000 MPa, more preferably at least1500 MPa, more preferably at least 2000 MPa, more preferably at least2500 MPa, and more preferably at least 3000 MPa. The ultimate strain ofthe reinforcing body or bodies is preferably at least 4%, morepreferably at least 6%, more preferably at least 10%, more preferably atleast 15%, more preferably at least 20%, and more preferably at 30%.These strong reinforcing bodies or components are preferably present ina high volume concentration in the reinforced composite structuredomain, e.g. typically at least 6% by volume as mentioned above, with agenuine three-dimensionality expressed by a volume concentration of atleast 1% in any specific direction of the domain. In a further preferredembodiment, the volume proportion of the reinforcing bodies in thedomain which has the reinforced composite structure is at least 8%,preferably at least 10%, such as at least 15%, e.g. at least 20%, suchas at least 25%, e.g. at least 30%, and the volume proportion of thereinforcing body or bodies in any specific direction of the domain is atleast 2%, e.g. at least 5%, e.g. at least 10%, such as at least 15%. Thevolume concentration of the reinforcement should, of course, not beconcentrated in a single reinforcement component. In a preferredembodiment, the number of reinforcing body components in the reinforcedcomposite structure domain is at least 8, such as at least 15, e.g. atleast 20, in any of the first, second and third dimensions of anarbitrary rectangular reference coordinate system in the reinforcedcomposite domain.

The matrix material of the shaped articles of the invention may beprepared by methods known as such in the art; for some of the matrixmaterials, more detailed descriptions of their preparation are givenherein. Important examples of matrices which are useful for the purposeof the invention are matrices comprising particles and fibres heldtogether by a binder, in particular ceramics-based materials,cement-based materials, plastics-based and glass-based materials.Particularly interesting materials are metal-based materials andcement-based materials. The latter types of materials comprise thematerials disclosed in the above-mentioned patent references.

For a matrix comprising matrix particles and fibres held together by abinder, e.g. a cement-based binder, the content of matrix particles andfibres in the matrix should be at least 50% by volume, e.g. at least 60%by volume, e.g. at least 70% by volume, e.g. at least 80% by volume,such as at least 85% or 90% by volume, and the content of fibres in thematrix should be at least 1% by volume, e.g. at least 2% by volume, e.g.at least 3% by volume, such as at least 5% or 10% by volume.

In a particular embodiment, when the matrix is prepared from a submatrixcomprising fine particles having a size of 0.5-100 mm (e.g. cementparticles), ultrafine particles having a size of from 50 Å to less than0.5 μm (e.g. microsilica particles), a dispersing agent (e.g. a concretesuperplasticizer) and water, the content of fine particles and ultrafineparticles in the submatrix should be at least 50% by volume, e.g. atleast 60% by volume, e.g. at least 65% by volume, e.g. at least 70% byvolume, such as at least 75% or 80% by volume, and the content of matrixparticles and fibres in the matrix should be at least 30% by volume,e.g. at least 40% by volume, e.g. at least 50% by volume, e.g. at least55% by volume, e.g. at least 60% by volume, e.g. at least 65% by volume,such as at least 70% or 75% by volume.

The combination of the matrix material with the main reinforcementshould be performed under conditions which ensure maximum density andhomogeneity of the matrix material tightly fixed to the reinforcement.Typically, the matrix material is introduced by casting in a mould inwhich the reinforcing system has been pre-arranged, the homogeneousdistribution of the matrix material in all interstices in thereinforcement and in excellent contact with the reinforcement preferablybeing aided by vibration or combined vibration and pressure, such asdescribed in the above-mentioned WO 87/07597.

Articles according to the present invention can be made in sizes fromsmall articles such as machine parts through sizes of the order of ameter or meters length and breadth up to even very large sizes with verythick walls of more than 30 cm, such as more than 50 cm or at least 75cm or at least one meter or even more. Such very large, thick-walledstructures are suitable, e.g., for encapsulation of nuclear powerstations.

Although the present description and drawings refer for the sake ofsimplicity to structures in which the reinforcement is found in planeswhich are substhantially perpendicular to each other, it will be clearthat the dimensions or planes defined by the reinforcement can be atvarious angles in relation to each other. Similarly, reinforcement inthe form of e.g. bars within a plane or layer is not necessarily alignedparallel to each other, but can be arranged as desired, as long as thebasic three-dimensional reinforcing structure of the invention,including the tension interlocking transverse rearrangement, isobtained. It should also be noted that the term “plane” as used in thepresent context should be understood to also refer to e.g. a curvedsurface. Thus, the “planes” of articles according to the invention maye.g. be the structure defined by inner and outer curves of an objectwith a semi-circular or other cross section which is not strictly“planar” in the geometric sense of the word.

The shaped articles of the present invention are typically in the formof e.g. plates, sheets, walls or portions thereof, etc., the surfaces ofwhich can, as indicated above, be planar or irregular, e.g. curved orangled in one or more dimensions. In such articles, the mainreinforcement will typically follow substantially, i.e. more or lessparallel with, the surfaces, while the transverse reinforcementtypically will extend more or less perpendicular to the surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section from the side of a composite articleaccording to the invention.

FIGS. 2 and 3 show cross sections from the side of alternativereinforcement structures in articles of the invention.

FIGS. 4 and 5 show views from above with alternative arrangement oftransverse reinforcement.

FIGS. 6 and 7 show side views and cross sectional views of differenttypes of transverse reinforcement.

FIGS. 8 and 9 show examples of perforated plates for use as transversereinforcement.

FIG. 10 shows a type of transverse reinforcement in the form of a singlebent plate or sheet containing a multiplicity of series of alignedholes.

FIG. 11 shows a view from the side illustrating the high velocity impactof a projectile in a material according to the invention.

FIGS. 12a, 12 b and 12 c show views from the side illustratingsuccessively the high velocity impact of a projectile in a reinforcedprior art material.

FIG. 13 shows a view from the side illustrating the effect of anexplosive impact on a reinforced prior art material.

FIGS. 14a and 14 b and 15 a and 15 b show schematically the behaviour ofmaterials according to the invention upon exposure to high velocityimpact.

FIGS. 16a and 16 b, 17 a and 17 b and 18 a, 18 b, 18 c, 18 d and 18 eshow schematically the behaviour of prior art reinforced materials uponexposure to high velocity impact.

The following drawings illustrate examples of how the reinforcement maybe arranged in different embodiments of the invention.

FIG. 1 shows an article according to the invention with mainreinforcement comprising three layers of reinforcing bars 4, 5 extendingin a first dimension X (perpendicular to the plane of the paper) and twolayers of reinforcing bars 2 extending in a second dimension Y.Reinforcing bars 4 in the two outer layers of bars in the X dimensionare tension interlocked by means of transverse reinforcing bars 6 whichextend in a third dimension Z substantially perpendicular to the planesdefined by the reinforcing bars 2 and the reinforcing bars 4, 5,respectively, and which wind around reinforcing bars 4 in the upper andlower layers.

The article shown in FIG. 1 can e.g. have a total thickness of 200 mm,reinforced with main reinforcing bars 2, 4, 5 of deformed steel 25 mm indiameter and with a transverse reinforcing bar 6 located at 100 mmintervals in the X dimension to tension interlock reinforcing bars 4.The reinforcement structure may in addition comprise further reinforcingbars (not shown) between the reinforcing bars 6 but offset 50 mm in theY dimension, thereby providing tension interlocking of those reinforcingbars 5 which are not shown in this figure as being interlocked with thetransverse reinforcing bars 6.

FIG. 2 shows another reinforcing structure similar to that shown in FIG.1, although in FIG. 2 the structure contains multiple layers ofreinforcing bars 2 extending in the first dimension and multiple layersof reinforcing bars 4 extending in the second dimension, with transversereinforcing bars 6 extending in the third dimension and winding aroundthe outer layers of reinforcing bars 4 to provide tension interlockingof the reinforcing structure.

FIG. 3 shows another reinforcing structure with multiple layers ofreinforcing bars extending in a first dimension (not shown) and multiplelayers of reinforcing bars extending in a second dimension (8, 10, 12,14; other layers not shown). In this structure, the transversereinforcement consists of 3 different layers of transverse reinforcingbars which together cooperate to interlock the outer layers ofreinforcing bars 8 and 14. Thus, transverse reinforcing bar 16interlocks reinforcing bar layers 8 and 10 (together with the bars, notshown, extending in the first and second dimensions and lying betweenbar layers 8 and 10), transverse reinforcing bar 18 interlocksreinforcing bar layers 10 and 12 (together with the bars, not shown,extending in the first and second dimensions and lying between barlayers 10 and 12), and transverse reinforcing bar 20 interlocksreinforcing bar layers 12 and 14 (together with the bars, not shown,extending in the first and second dimensions and lying between barlayers 12 and 14).

FIGS. 4 and 5 show examples of reinforcing structures e.g. as describedwith reference to FIG. 1 or 2 from above. The two figures show differentexamples of the placement of the transverse reinforcing bars 6 whichwrap around and interlock the reinforcing bars 4.

FIGS. 6 and 7 shows examples of different types of transversereinforcement suitable for interlocking reinforcing bars. In FIG. 6 thetransverse reinforcement has a substantially round cross-section and isin the form of a thick circular wire/bar or a substantially circularcable formed from a multiplicity of wires. In FIG. 7 the transversereinforcement has a rectangular cross-section and is in the form of asolid rectangular bar or a rectangular bar comprising a multiplicity ofwires.

FIGS. 8 and 9 show examples of perforated plates designed to providetension interlocking to a series of bars extending through the holes inthe plates. In FIG. 8 the plate contains a multiplicity of circularholes, each of which is adapted to have a single bar extend through thehole. In FIG. 9 the plate contains a multiplicity of oblong holes, eachof which is adapted to have two or more bars extend through the hole.

FIG. 10 shows an example of the transverse reinforcement in the form ofa single bent plate or sheet containing a multiplicity of series ofaligned holes, each series of aligned holes being designed toaccommodate a single reinforcing bar. The bent plate or sheet furtherdefines a series of upper and lower bays 22, 24, each of which isadapted to hold a reinforcing bar. In this structure, the transversereinforcement thus holds a single layer of reinforcing bars extending ina first dimension through the aligned holes and two layers ofreinforcing bars extending in a second dimension through the upper andlower bays 22, 24.

The matrix in the shaped articles of the present invention may beprepared from a number of different types of materials, includingcement-based materials and metallic materials.

Metallic matrices in shaped articles according to the invention may bebased on metal such as aluminium, copper, tin, lead, etc. or alloys suchas aluminium alloys. When the matrix is based on a metal or alloy, thereinforcement will typically be of a material with a substantiallyhigher strength than the strength of the matrix metal or alloy, e.g.steel with a tensile strength of at least 700 MPa and preferably as highas e.g. 3000 MPa. For processing reasons, the reinforcement in the caseof a metal or alloy matrix should also have a substantially highermelting point and recrystallisation temperature than that of the matrixmaterial.

A preferred metal for the matrix of the present invention will often bealuminium or an alloy thereof, aluminium being preferred because it hasa number of advantageous properties. In the following, aluminium andalloys thereof are used by way of example to illustrate metal matrixbased composites according to the invention, with high-quality alloysteel as an example of a suitable reinforcing material. Metal matricesbased on aluminium meet to a substantial degree the general materialrequirements for matrix materials of the invention, e.g. in terms ofrigidity (about 70 GPa), modulus of elasticity, fracture energy (about10-30 kN/m) and compressive strength (200 MPa or more). Aluminium alsohas a relatively high tensile ductility: 5-30% for aluminium alloys and50% for pure aluminium.

This combination of high strength, relatively high rigidity and hightoughness, both in bulk and upon fracturing, makes the combination of analuminium-based matrix and strong steel reinforcement particularlysuited to obtain the desired mechanical behaviour of articles accordingto the invention. Aluminium and alloys thereof also have otherproperties that make them desirable for use in articles according to theinvention, for example a low density which is about ⅓ the density ofsteel. The relatively low—but not excessively low—melting point ofaluminium also makes aluminium and alloys thereof interesting for anumber of applications. This allows e.g. processing by casting, possiblypressure casting, under conditions that allow the use of high qualityreinforcement, e.g. high quality alloy steel, without or with onlyminimal thermal damage to the reinforcement during casting. Although themelting point of aluminium is significantly lower than that of e.g.steel, it is nevertheless sufficiently high (660° C. for pure aluminium)to ensure good performance over a broad temperature range.

Articles according to the invention with unique mechanical propertiescompared to articles of similar shape but made of monolithichigh-quality steel, and with a density of only about 40-70% of that ofsteel, are suitable for use in e.g. cars, ships and planes to reinforceand protect against collision impact.

Metal matrices according to the invention may, however, also be based onmaterials having characteristics different from those of aluminium andaluminium alloys. For example, “soft” matrices based on tin, tin alloys,lead or lead alloys may be of interest for uses in which a large tensileductility is desired. In this case, the modulus of elasticity andcompressive strength may be somewhat lower than that which is otherwiserequired for articles of the invention (e.g. as set forth in claim 1),as long as this is balanced by a very high tensile ductility. Suchmaterials may thus be characterised by a compressive strength of atleast 15 MPa, preferably at least 25 MPa, more preferably at least 35MPa, still more preferably at least 50 MPa, most preferably at least 80MPa, a modulus of elasticity of at least 10 GPa, preferably at least 15GPa, more preferably at least 25 GPa, most preferably at least 40 GPa,and a tensile ductility of at least 0.2 kN/m, preferably at least 0.3(30%), more preferably at least 0.4, more preferably at least 0.5, morepreferably at least 0.7, most preferably at least 0.8.

Another interesting aspect of the invention relates to shaped articleswith metal- or alloy-based matrices in which the matrix materialsprovide the articles with specific non-mechanical properties such ashigh or low thermal conductivity, electrical conductivity, magneticpermeability, etc. A type of shaped article of particular interest isone whose matrix has a large resistance against radioactive radiation,e.g. a matrix based on lead.

In any shaped article according to the invention, including those withmetal matrices as described above as well as cement-based matrices asdescribed below, it is of particular interest to include in the matrixstrong particles, fibres or whiskers, e.g. Al₂O₃ particles, SiC whiskersor steel fibres. Further examples of materials of which such strongparticles, fibres or whiskers may be composed are carbides, oxides,nitrides, silicides, borides, metals and graphite, including TiC, ZrC,WC, NbC, AlN, TiN, BN, Si₃N₄, MgO, SiO₂, ZrO₂, Fe₂O₃, Y₂O₃, tungsten,molybdenum and carbon.

In addition to a metal matrix such as an aluminium or aluminium alloybased matrix, another presently preferred matrix is a cement-basedmatrix prepared from cement, typically Portland cement or refractorycement, ultrafine particles, in particular ultrafine silica dustparticles (microsilica), fibres, a dispersing agent, in particular aconcrete superplasticizer, and water.

One such cement-based matrix is described in EP 010777, which disclosesstrong and dense cement-based composite materials containing a matrix ofultrafine silica particles (A) of a size of from 50 Å to 0.5 μmhomogeneously arranged to fill the voids between densely packed fineparticles (B) of a size of 0.5-100 μm, at least 20% and typically atleast 50% of the particles B being Portland cement particles. The amountof ultrafine silica particles A in the matrix is quite large, i.e. inthe range of 5-50% by volume, typically 10-30%, based on the totalvolume of particles A+B. The material is further characterized by a verylow water/powder ratio, i.e. 0.12-0.30 and preferably 0.12-0.20 byweight based on the weight of particles A+B, which is made possible byuse of a large amount of a concrete superplasticizer, i.e. 1-4% byweight of superplasticizer dry matter, typically 2-4%, based on theweight of the cement and silica dust. The fibres may e.g. be selectedfrom metal fibres, including steel fibres, mineral fibres, includingglass fibres, asbestos fibres and high temperature fibres, Kevlarfibres, carbon fibres, and organic fibres, including plastic fibres. Thefibres may also comprise e.g. fibres or whiskers of silicon carbide,boron, graphite or alumina. For purposes of the present invention, metalfibres, in particular steel fibres, are presently preferred, althoughother types of fibres, in particular high strength fibres such as Kevlarfibres or silicon carbide fibres or whiskers, may also be used. As isdescribed in EP 010777, the mixture of the various components normallyappears unusually dry due to the relatively small amount of water whichis used, and mixing must therefore be performed for an extended periodof time compared to conventional concrete mixes in order to obtain a mixwith a fluid to plastic consistency and with the desired dense packingof the particles B with the ultrafine silica particles A in the voidsbetween the densely packed particles B.

Preferably, the aggregate used in cement-based matrixes of this type isa strong aggregate as described in EP 042935. The strong aggregate maybe described as comprising particles having a size of 100 μm-0.1 m and astrength corresponding to at least one of the following criteria:

1) a compaction pressure of above 30 MPa at a degree of compaction of0.70, above 50 MPa at a degree of compaction of 0.75, and above 90 MPaat a degree of compaction of 0.80, as assessed by uniaxial die pressingon initially loosely packed particles of the material having a sizeratio between the largest and smallest particle substantially notexceeding 4,

2) a Moh's hardness (referring to the mineral constituting theparticles) exceeding 7, and

3) a Knoop indentor hardness (referring to the mineral constituting theparticles) exceeding 800.

Examples of such strong aggregate particles are topaz, lawsonite,diamond, corundum, phenacite, spinel, beryl, chrysoberyl, tourmaline,granite, andalusite, staurolite, zircon, boron carbide, tungstencarbide, silicon carbide, alumina and bauxite. A preferred strongaggregate material is refractory grade bauxite.

A preferred matrix for the shaped articles of the present invention isin particular one which makes use of the principles described in WO87/07597. As mentioned above, this reference discloses a compactreinforced composite (CRC) material comprising a base matrixcorresponding to the composite materials described in EP 010777 and EP042935, this base matrix being reinforced with a high content ofrelatively fine fibres and further reinforced with a high content ofmain reinforcement in the form of e.g. steel bars, wires or cables.

The CRC structure may be described as a shaped article in which thearticle itself, the matrix comprising the main reinforcement or the basematrix has a high stiffness in any direction as defined by at least oneof the following criteria:

1) the modulus of elasticity in any direction being at least 30,000 MPa,preferably at least 50,000 MPa, or

2) the resistance to compression in any direction being at least 80 MPa,preferably at least 130 MPa, the matrix containing fibres in a volumeconcentration of at least 2%, preferably at least 4%, typically at least6%, e.g. 10% or more, based on the volume of the matrix,

and the volume concentration of the main reinforcement in the tensilezone or zones of the article being at least 5%, preferably at least 7%,typically at least 10%, e.g. at least 15%.

When the CRC structure has a cement-based matrix, it provides a materialwith a strength like that of structural steel, while at the same timeproviding the advantages of a composite material. This allows theachievement of various desirable properties not available with materialssuch as steel, for example chemical resistance, and further allows theconstruction of large, massive structures for which conventionalmaterials such as steel or conventional reinforced concrete areunsuitable. The main principle upon which the CRC structure is based isthus the combination of a relatively large amount of heavy mainreinforcement embedded in a fibre-reinforced matrix which is strong andvery rigid, but also very ductile in spite of the fact that thecement-based base matrix material per se is hard and brittle. The CRCmaterials thus function in a similar manner to conventional reinforcedconcrete, i.e. the pressure load is predominantly carried by thefibre-reinforced matrix and the tensile load is predominantly carried bythe main reinforcement, the fibre-reinforced matrix transferring forcesbetween the components of the main reinforcement. Such CRC materials,with their unique combination of a strong base matrix and a high contentof main reinforcement, are able to resist much greater loads thanconventional steel-reinforced concrete and are therefore suitable for awealth of applications for which conventional reinforced concrete isunsuitable.

The CRC materials described in WO 87/07597 show a unique combination ofstrength, rigidity and ductility and are well-suited for very largeload-bearing structures. However, they do not include the tensioninterlocked main reinforcement which is a key feature of the hard impactresistant composites of the present invention.

As mentioned above, the intricate arrangement of the reinforcementaccording to the present invention was not contemplated or suggested inWO 87/07597, despite the emphasis in this document on the properties ofboth the matrix and the reinforcement. This is related to the fact thatthe CRC materials as described in WO 87/07597 were found to provide suchdramatic improvements compared to e.g. ordinary reinforced concrete, forexample in bending tests, that a special transverse reinforcement suchas that according to the present invention was clearly not considered asa possibility.

Although these CRC structures without any transverse reinforcement 5were found to perform extremely well compared to ordinary reinforcedconcrete, the possible use of transverse reinforcement in the form ofshort, straight bars is discussed at pages 67-70 of WO 87/07597 inconnection with plates designed for resistance to explosion or impactwith strongly concentrated loads, in order to obtain an even betterperformance under such conditions. It is worth noting, however, that theonly type of transverse reinforcement that is suggested is in the formof very short (length 100 mm) straight bars placed perpendicular to mainreinforcing bars (cf. FIGS. 17b and 46 of this document). There is nosuggestion to use any kind of interlocking transverse reinforcement orany other kind of transverse reinforcement, nor is there anything inthis document that would motivate a person skilled in the art to use anytype of interlocking transverse reinforcement, especially given thedescription in WO 87/07597 (Example 7) of how even very short bars areeffectively anchored in the CRC structure.

In fact, explosion impact tests performed after the publication of WO87/07597 and using an explosive charge of 3 kg showed that although CRCplates containing 100 mm transverse reinforcing bars performedremarkably well compared to normal reinforced concrete (which wascompletely destroyed by even a much smaller amount of explosive), theynevertheless suffered significant damage in the immediate vicinity ofthe explosion. The tests with the CRC plates are described below withreference to FIG. 13, and they are also described in the publication “NyBeton—Ny Teknologi”, available from Aalborg Portland, Denmark. Thus,even though the CRC structures described in WO 87/07597 provided quiteremarkable results in terms of resistance to concentrated loads such asexplosions, there is still room for improvement in ways not contemplatedby WO 87/07597.

Test Methods

Where reference is made herein to the compressive strength, modulus ofelasticity and fracture energy of matrix materials according to theinvention, these properties may be determined on matrix material samples(i.e. samples prepared without reinforcement) as follows:

Matrix Compressive Strength

The compressive strength is determined on a cylindrical sample of thematrix material with a diameter of 10 cm and a height of 20 cm, using aconventional static test arrangement with a slowly increasing load.

Matrix Modulus of Elasticity

The modulus of elasticity is determined on the basis of stress-straincurves obtained from compression tests on cylindrical samples (diameter10 cm, height 20 cm).

Matrix Fracture Energy

The fracture energy is determined using 3-point bending tests accordingto the RILEM TC 50—FCM recommendations. The beams have dimensions of100×100×840 mm with a central notch having a depth of 50 mm. The beamsare supported symmetrically using two supports separated by a distanceof 800 mm and are loaded with a single central force.

It is also possible to obtain a rough approximation of the matrixcompressive strength and modulus of elasticity on shaped articlesaccording to the invention (i.e. articles containing reinforcement). Forexample, the approximate compressive strength of a matrix material canbe determined by surface penetration measurements in which a hard objectis pressed into the material. The approximate modulus of elasticity canfor example be determined using acoustic measurements or oscillationmeasurements.

In this case, the conversion to standard values is performed taking intoconsideration the effect of the reinforcement as well as known orestimated relationships between the results of measurements performed inthis manner and the results of measurements performed using standardtest methods.

The tensile strength and ultimate strain of the reinforcing bodies canbe determined using conventional tensile tests with a slowly increasingload, typically according to standard procedures for the reinforcementin question. Although it is possible to perform measurements onreinforcement that has been mechanically removed from a shaped articleprepared according to the invention, determination of reinforcementproperties will preferably be performed on separate reinforcing bodiesof the same type as those used in the shaped article in question.

Measurements on shaped articles according to the invention, or on matrixmaterials or reinforcing bodies used for such shaped articles, willtypically be performed at ambient temperature, i.e. typically at about20° C.

The invention will be further illustrated in the following non-limitingexamples.

EXAMPLES Example 1

This example describes articles according to the invention, namely 5plates each having outer dimensions of 1500×1500×200 mm.

The example shows:

1. the construction/design of the articles, including structure of thematrix material and the binder;

2. the composition of the matrix material and the type and amount of thedifferent components;

3. preparation of the plates:

a) processes for mixing the components which form the hard, rigid, toughmatrix materials,

b) mixing of the matrix materials (in a fluid to plastic condition) withthe dense and strong three- dimensional reinforcing structure of thearticles, and

c) solidifying the matrix materials; and

4. the behaviour of the articles according to the invention whensubjected to a very large high velocity impact (being hit by anarmour-piercing shell weighing 47 kg with an impact speed of 482 m/sec).

Construction of the Articles

5 plates, each having dimensions of 1500×1500×200 mm, were prepared. Thereinforcement is as shown in FIG. 1. The articles contain mainreinforcement arranged in 2 dimensions in the plane of the plates in theform of straight bars of deformed steel (“kamstål”) with a diameter of25 mm with 3 layers of bars in the X direction and 2 in the Y direction.The distance between the reinforcing bars in both the X and Y directionis 50 mm, referring to the distance between the centres of the bars (inother words 25 mm between the edges of the bars). The main reinforcementis spatially bound together by transverse reinforcement which functionsin the transverse direction of the plates. The transverse reinforcementconsists of long deformed steel bars with a diameter of 10 mm which arebent as shown in FIG. 1 with straight parts and curved parts, the curvedparts having a curve radius of about 25 mm.

The transverse reinforcement at the top winds closely around the upperreinforcing bars and at the bottom around the lower bars (“top” and“bottom” here being with reference to the top and bottom planes of theplates during production thereof). The curved transverse reinforcingbars hold each of the reinforcing bars in the 100 mm layer of mainreinforcement (100 mm between the centre of the top and bottom bars)together. This arrangement is obtained with the transverse reinforcingbars arranged so that every other transverse reinforcing bar is offset50 mm in the Y direction. This ensures the arrangement shown in FIG. 1where all of the top and bottom reinforcing bars are intimatelyconnected. The vertical parts of the transverse reinforcing bars betweenthe top and bottom reinforcement are oriented substantiallyperpendicular to the plane of the plates, in other words substantiallyin the Z direction.

The deformed steel reinforcing bars for both the main reinforcement (25mm diameter) and the transverse reinforcement (10 mm diameter) has astated yield value of above 410 MPa. The yield stress is estimated to be500-510 MPa, the rupture stress (tensile strength) 610 MPa, and thestrain at rupture 25% in the rupture zone measured on a length 10 timesthe diameter and 14% outside the rupture zone.

Matrix

The matrix material fills substantially the space limited by 1) thefinished article's outer spatial dimensions, in other wordscorresponding to the internal dimension in boxes measuring 1500×1500×200mm internally, and 2) the reinforcement described above, whichsubstantially fills the space defined by these dimensions. (Estimatedtrapped air: at the most 1-2% by volume.)

The matrix is prepared from:

1) strong particles of calcined bauxite having sizes in the ranges of0-2 mm and 5-8 mm,

30 2) strong short steel fibres (length 12 mm, diameter 0.4 mm),

3) a strong and dense so-called DSP binder of the type described in EP010777 comprising Portland cement, microsilica and a concretesuperplasticizer, and

4) water.

The volume proportions are:

bauxite particles 51.6% steel fibres  4.0% binder   30% water  14.4%.

The binder is an extremely strong, hard and dense material formed bysolidification of a material prepared from cement particles (median sizeabout 10 μm) (the “fine particles”) and microsilica (median size 0.1-0.2μm) (the “ultrafine particles”) arranged in a very homogeneous and verydense configuration with liquid (water containing dissolved dispersingagents) substantially filling the space between the densely packed fineand ultrafine particles.

The “submatrix” containing cement, microsilica and superplasticizercontains approximately 79% by weight of cement, 20% by weight ofmicrosilica and 1% by weight of superplasticizer.

Upon solidification, a part of the cement and some of the microsilicaform a chemical compound with the liquid, thereby forming a strong,dense “glue” which binds the non-chemically reacting parts in a verydense and strong structure. The “glue” which is formed (mainly calciumsilicate hydrates) fills a substantially larger volume than the volumeof the dry matter which has been reacted. This results in a very densesolid structure with a very small internal porosity, i.e. a porositysubstantially less than the porosity of the material before the chemicalreaction.

The matrix was prepared by mixing together INDUCAST 6000 GT from DensitA/S (Aalborg, Denmark), bauxite 5-8 mm, steel fibres and water. The mixcomposition of the complete matrix was: INDUCAST 6000 GT, 1486.24 kg;bauxite, 1023.63 kg; water, 142.72 kg; steel fibres, 307.09 kg.

The mixing was performed in a large forced action mixer for 7-8 minutesfor each of the 5 plates of 1500×1500×200 mm. Dry mixng without fibreswas performed for about 2 min, followed by addition of water and mixingfor about 10 min and then addition of fibres and additional mixing forabout 5 min. Casting took place on a vibration table using vibration.Hardening of the plates took place in a “hot tent” covered with plastic,at a temperature of about 40° C. for 7 days.

The hardened matrix material has the following properties (estimatedvalues based on the inventor's previous experience with the same type ofmatrix material):

compressive strength 225-250 MPa modulus of elasticity 60-80 GPa static70-90 GPa dynamic fracture energy 15-30 kN/m density 2900 kg/m3

Testing of the Plates

Shaped articles in the form of plates prepared as described above weresubjected to a test to determine their ability to resist high velocityimpact of a non-exploding armour-piercing shell with a steel tip. Theshell had a diameter of 152 mm, a weight of 47 kg and an impact speed of482 m/sec. (It is interesting to note that although the shell wasnon-exploding, it did in fact contain 2.5 kg of explosive at the back ofthe shell, but no detonator, and it was found that the explosive uponimpact was thrown backwards about 100 m).

The test arrangement is shown in FIG. 11. The 5 test plates, each havinga thickness of 200 mm, were fastened to each other using strong bolts toprovide an article in the form of a composite block having a totalthickness of 1000 mm. This article was shot in the centre with thearmour-piercing shell fired from a cannon at a distance of 100-200 m.

As a control, cement based plates with the same dimensions and placed inthe same arrangement with 5 plates fastened together were tested in thesame manner. These control plates were prepared from a very strong anddense cement-based material corresponding to that which is describedabove with reference to EP 010777. They contained about 3-5% by volumeof steel fibres, of which some had lengths of 6-12 mm and some hadlengths of up to 40 mm, and 20-30% of aggregate comprising bauxiteparticles as well as larger (up to about 16 mm) particles of granite.The control plates did not contain a steel bar reinforcement, but theywere prepared using a square steel frame at the edges of the plates.

The control plates, despite being of a material which is extremelystrong and durable under normal, static conditions, showed “normal”behaviour with very extensive damage after being hit by the shell. Thefirst plate had a very large hole in it, and material from this platewas expelled backwards to the side and up. The second plate was evenmore damaged than the first, with the sides being pushed out and theupper approximately ⅕ of the plate being blown away. In both the firstand second plates, the steel frame surrounding the plates was blown topieces. The projectile stopped in the back of the third plate, whichalso suffered extensive damage. Plate 4 was also damaged, although lessso than the other plates. Plate 5 had a partial hole, with a cone shapedpiece pushed out and back a distance of about 20 cm, and with 4 largecracks extending from the centre towards the corners, the cracks havingopenings of about 5 cm.

As illustrated in FIG. 11, the composite block composed of platesaccording to the invention suffered only a minimal amount of damage as aresult of this high velocity impact. The 47 kg shell, which had a lengthof about 0.5 m, penetrated only the first 2 plates, where it ended beinglodged with about 8 cm of the back end extending out of the first plate.Other than this local penetration and some damage to the matrix in theimmediate vicinity of the impact, the article was essentially undamageddespite the extremely large amount of energy carried by the shell uponimpact. The damage of the matrix in the immediate vicinity of the impactconsisted of surface damage of matrix material lying outside thereinforcement, this damage extending to a depth of about 10-20 mm andhaving a diameter of about 30-40 cm. Outside of this zone, fine radialcracks were seen in the otherwise apparently undamaged front surface ofthe first plate extending outwards from the shell in the direction ofthe edges of the plate. In the vicinity of the shell, the top of thetransverse reinforcement and a portion of the top layer of mainreinforcement was visible.

Example 2

2 plates having outer dimensions of 500×500×100 mm were prepared in amanner similar to that described in Example 1, i.e. 3+2 layers of mainreinforcement in the form of deformed steel bars interlocked withtransverse reinforcement also in the form of steel bars wrapped aroundthe outer layers of main reinforcement. In this case, however, the mainreinforcing bars had a diameter of 12 mm and the transverse reinforcingbars had a diameter of 6 mm. The matrix was substantially as describedin Example 1, although with the steel fibres being 0.15×6 mm (tensilestrength 2900 MPa) and the aggregate being SiC instead of bauxite and ofa slightly smaller particles size than the bauxite particles of Example1.

The plates were not subjected to impact testing, but this exampleillustrates the possibility, in relation to Example 1, to upscale ordownscale the size of the shaped articles prepared according to theinvention.

Example 3 (Comparative Example)

The behaviour of materials is in many ways fundamentally different underhigh velocity impact than under the effect slow static forces, highvelocity impact often resulting in fatal failure or destruction ofarticles which otherwise have very high load bearing capabilities understatic conditions. FIGS. 12a, 12 b and 12 c show a very strong, toughand hard article made from an extremely strong and tough DSP materialwhose matrix includes Al₂O₃ rich particles of a size of 1-4 mm and 4% byvolume of steel fibres, the article being reinforced with about 25% byvolume of strong steel bars (deformed steel) with a diameter of 25 mm,the distance between the centres of two adjacent bars in the samedimension being 50 mm. The article is composed of 5 individual plates,each having a thickness of 200 mm. Such plates are extremely strongunder static conditions, e.g. having a bending strength in the Ydirection in the range of 200-250 MPa and about 50-100 MPa in the Xdirection. However, under high velocity impact with a 4.5 kg tungstenprojectile having a diameter of 50 mm and an impact speed of about 1400m/sec, the material from the first 2 plates was shattered and violentlycast backwards (see FIG. 12b +12 c).

Under this high velocity impact, very powerful shock waves were created,which in turn induced very powerful tensile effects that totallyshattered the effected plates. In spite of their extremely high staticstrength and very high degree of steel bar reinforcement, these platesshowed very poor resistance to these high velocity tensile effects.

Example 4 (Comparative Example)

FIG. 13 shows a cross section of an extremely strong and toughreinforced cement-based plate according to the prior art. This plate isformed from a strong and tough DSP material with very strong aggregateparticles (Al₂O₃ rich sand) and a high volume concentration of strongfine fibres (6% by volume of steel fibres 0.15×6 mm with a tensilestrength of 2900 MPa). These plates contained about 20% by volume ofmain reinforcement (deformed steel bars, diameter 16 mm) in the plane ofthe plates. The plates contained 35 in addition transverse reinforcementin the form of 100 mm long deformed steel bars with a diameter of 10 mmin the Z (transverse) direction for each 40 mm in the X and Ydirections, 7% by volume. These transverse reinforcing bars wereconnected to the main reinforcement above by welding and resulted in asignificant positive effect in experiments under static conditions.

The behaviour of these plates when subjected to the force of 3 kg ofexplosive was exceptionally good and was comparable in many ways to thatof a 70 mm sheet of steel. While reacting much better than similarplates without the transverse reinforcing bars, they still sufferedconsiderable damage, however. As shown in FIG. 13, the explosion(indicated by the star) resulted in damage in the form of a considerabledelamination of the centre zone on the back side, where the outer layerof reinforcement after the explosion was bent about 40 mm away from itsoriginal position. The explosion also resulted in a powerful expulsionof most of the 100 mm long transverse reinforcing bars (also shown inFIG. 13), despite the fact that these bars were welded to the mainreinforcement. Although the transverse reinforcement in this caseundoubtedly had an effect in terms of stabilising the plate and holdingthe material within a certain distance from the explosion zone, theplate nevertheless suffered considerable damage.

Example 5

FIGS. 14a and 14b and 15 a and 15 b show schematically two differentreinforcing systems according to the present invention and how thesesystems react under high velocity impact, while FIGS. 16-18 showexamples of prior art reinforcing systems and how these react under highvelocity impact.

FIGS. 14a and 14 b and 15 a and 15 b show cross sections ofreinforcement according to the invention with a top layer of mainreinforcement 1 and a bottom layer of main reinforcement 2. (As showne.g. in FIGS. 1-3, there will typically be several layers of mainreinforcement, as well as main reinforcement extending both in the planeof the paper and perpendicular thereto, but for the sake of simplicityonly the top and bottom layers of main reinforcement are shown in thefigures related to this example).

This example shows the effects of subjecting the various plates orplates shown to a momentary high velocity impact from above, e.g. bymeans of an explosive as described in Example 4. The pressure impulse isreflected at the bottom side in a tension impulse which creates a lowerzone 3 moving downward at a high speed. The zone 3 would be flung awayfrom the upper part in the absence of the transverse reinforcement 4according to the invention, which ensures that the reinforcing system ismechanically interlocked, in this case with respect to influencesperpendicular to the plane of the plate.

The upper reinforcing bars 1 are individually fixed to individual lowerreinforcing bars 2 by the tension-based interlocking of the transversereinforcement 4. This means that failure of the article only can takeplace after the transverse reinforcement 4 has been broken in tension.By fixating and mechanically holding together all of the outerreinforcing bars with effective tension connections between the twoouter layers, a complete mechanical fixation of the intermediatereinforcing layers (not shown) is also obtained (e.g. as shown in FIG.1).

FIGS. 14a and 15 a show the situation before the lower zone 3 has movedrelative to the upper zone. FIGS. 14b and 15 b show the situationshortly after the explosion, when the lower zone 3 has moved the maximumamount relative to the upper zone. In this theoretical example, thematrix material has failed in FIGS. 14b and 15 b, resulting in theformation of cracks or openings 5, but the interlocking transversereinforcement 4 prevents total failure of the article by holding theupper main reinforcement 1 and the lower main reinforcement 2 togetherin tension. In FIGS. 14b and 15 b, the transverse reinforcement 4 hasthus become longer (and thinner) than was the case in FIGS. 14a and 15a.

The prior art plates shown in FIGS. 16a and 16 b, 17 a and 17 b and 18a, 18 b, 18 c, 18 d and 18 e also contain upper and lower layers of mainreinforcing bars together with transverse reinforcement 6, 7, 8, but thetransverse reinforcement does not provide effective mechanical tensioninterlocking of the main reinforcing bars in the respective systems.

In FIGS. 16a and 16 b and 17 a and 17 b the transverse reinforcementdoes not provide any mechanical interlocking of the main reinforcement.When the matrix fails in these systems (shown in FIGS. 16b and 17 b),the transverse reinforcement provides no additional coherence for thearticle, and the result is total failure. In FIG. 17b, where thetransverse reinforcement is in the form of straight bars, there is eventhe risk that the transverse reinforcement can be dangerous, since thesetransverse bars 9 can be “shot out” of the article by the pressureimpulse, as described in Example 4.

In FIGS. 18a, 18 b, 18 c, 18 d and 18 e the transverse reinforcement 8provides a certain mechanical interlocking of the upper and lower mainreinforcing bars, but this is not tension-based interlocking. As aresult, the transverse reinforcement fails upon bending, and thistypically takes place at impact effects which are orders of magnitudesmaller than that which can be tolerated by the tension-basedinterlocking reinforcement of the present invention. FIGS. 18a-18 e showsuccessively an increasing degree of failure of the transversereinforcement by bending of the bottom part of the transversereinforcement, which in the beginning is curved around the lowerreinforcing bar, until the bottom part of the transverse reinforcementhas essentially lost its curvature and thus lost its grip on the bottomreinforcing bar. At this point, FIG. 18e, the result is a total failureof the material.

What is claimed is:
 1. A shaped article, at least one domain of whichcomprises a three-dimensionally reinforced composite structure thatcomprises a matrix and a reinforcing system, the reinforcing systemcomprising a plurality of bodies embedded in the matrix and extendingthree-dimensionally in first, second and third dimensions therein, thereinforcing system being tension interlocked in at least one dimensionin that reinforcement components extending in at least one of the firstand second dimensions are tension interlocked to reinforcementcomponents extending in the same dimension(s), but at a transversedistance therefrom, by transverse reinforcement components extending ina dimension transverse to a plane or surface defined by thereinforcement in the at least one of the first and second dimensions,wherein the matrix has a compressive strength of at least 80 MPa, amodulus of elasticity of at least 40 GPa, and a fracture energy of atleast 0.5 kN/m, the reinforcing bodies having a tensile strength of atleast 200 MPa, and the volume proportion of the reinforcing bodies inthe reinforced composite structure being at least 2%, the volumeproportion in any specific direction being at least 0.5%.
 2. The shapedarticle of claim 1 wherein the volume proportion of the reinforcingbodies in the reinforced composite structure is at least 4%, the volumeproportion in any specific direction being at least 0.75%.
 3. The shapedarticle of claim 2 wherein the volume proportion of the reinforcingbodies in the reinforced composite structure is at least 6%, the volumeproportion in any specific direction being at least 1%.
 4. The shapedarticle of claim 1 wherein the number of reinforcing components in thereinforced composite structure domain is at least 3 in any of the first,second and third dimensions of an arbitrary rectangular referencecoordinate system in the reinforced composite domain.
 5. The shapedarticle of claim 1 wherein the ultimate strain of the reinforcing bodiesis at least 2%, with the proviso that when the reinforcing bodies have atensile strength between 200 and 300 MPa then the ultimate strain is atleast 20%, and when the reinforcing bodies have a tensile strengthbetween 301 and 400 MPa, then the ultimate strain is at least 15%. 6.The shaped article of claim 5 comprising reinforcement componentscomprising bars extending in the first and second dimensions, at leastbars of outermost opposite planes or surfaces of the reinforcement beingtension interlocked by transverse reinforcement components extending inthe third dimension.
 7. The shaped article of claim 5 comprisingreinforcement components in the form of bars extending in at least oneof the first and second dimensions, at least bars of outermost planes orsurfaces of the reinforcement being tension interlocked in at least onedirection by being fixed in perforations of perforated plates extendingin the second and third dimensions.
 8. The shaped article of claim 1wherein the transverse reinforcement components tension interlockreinforcement components of opposite outermost or substantiallyoutermost planes or surfaces of the reinforcement, each of saidsubstantially outermost reinforcement planes or surfaces being definedby reinforcement components extending in at least one of the first andsecond dimensions.
 9. The shaped article of claim 1, wherein the matrixmaterial has a compressive strength of at least about 100 MPa.
 10. Theshaped article of claim 1, wherein the matrix material has a modulus ofelasticity of at least about 60 GPa.
 11. The shaped article of claim 1,wherein the matrix material has a fracture energy of at least about 1kN/m.
 12. The shaped article of claim 1, wherein the reinforcing bodieshave a tensile strength of at least about 400 MPa.
 13. The shapedarticle of claim 1, wherein the ultimate strain of the reinforcingbodies is at least about 4%.
 14. The shaped article of claim 1, whereinthe volume proportion of the reinforcing bodies in the domain which hasthe reinforced composite structure is at least about 8% and the volumeproportion of the reinforcing bodies in any specific direction of thedomain is at least about 2%.
 15. The shaped article of claim 1 whereinthe number of reinforcing components in the reinforced compositestructure domain is at least 8 in any of the first, second and thirddimensions of an arbitrary rectangular reference coordinate system inthe reinforced composite domain.
 16. The shaped article of claim 15wherein the matrix further contains a strong aggregate comprisingparticles having a size of 100 μm-0.1 m and a strength corresponding toat least one of the following criteria: 1) a compaction pressure ofabove 30 MPa at a degree of compaction of 0.70, above 50 MPa at a degreeof compaction of 0.75, and above 90 MPa at a degree of compaction of0.80, as assessed by uniaxial die pressing on initially loosely packedparticles of the material having a size ratio between the largest andsmallest particle substantially not exceeding 4, 2) a Moh's hardness(referring to the mineral constituting the particles) exceeding 7, and3) a Knoop indentor hardness (referring to the mineral constituting theparticles) exceeding
 800. 17. The shaped article of claim 16, whereinthe strong aggregate particles are selected from topaz, lawsonite,diamond, corundum, phenacite, spinel, beryl, chrysoberyl, tourmaline,granite, andalusite, staurolite, zircon, boron carbide, tungstencarbide, silicon carbide, alumina and bauxite.
 18. The shaped article ofclaim 1 wherein the matrix comprises matrix particles and fibers heldtogether by a binder, the content of matrix particles and fibers in thematrix being at least about 50% by volume, and the content of fibers inthe matrix being at least about 1% by volume.
 19. The shaped article ofclaim 18, wherein the content of matrix particles and fibers in thematrix is at least about 60% by volume, and the content of fibers in thematrix is at least about 2% by volume.
 20. The shaped article of claim 1wherein the matrix is prepared from a submatrix comprising fineparticles having a size of 0.5-100 μm, ultrafine particles having a sizeof from 50 Å to less than 0.5 μm, a dispersing agent and water.
 21. Theshaped article of claim 20, wherein the fine particles comprise cementparticles, the ultrafine particles comprise microsilica particles andthe dispersing agent comprises a concrete superplasticizer.
 22. Theshaped article of claim 1, wherein the matrix is based on a metal oralloy.
 23. The shaped article of claim 22, wherein the matrix is basedon aluminium or an aluminium alloy.
 24. The shaped article of claim 1,wherein the reinforcing bodies are selected from the group consisting ofbars, cables, wires and plates.
 25. The shaped article of claim 1,wherein the reinforcing bodies comprise steel bodies.
 26. The shapedarticle of claim 25, wherein the reinforcing bodies exhibit at least oneof the following characteristics: (a) a tensile strength of at leastabout 1000 MPa; and (b) an ultimate strain of at least about 10%. 27.The shaped article of claim 1, wherein the reinforcing bodies exhibit atleast one of the following characteristics: (a) a tensile strength of atleast about 700 MPa; and (b) an ultimate strain of at least about 6%.28. The shaped article of claim 1, wherein the matrix exhibits at leastone of the following characteristics: (a) a compressive strength of atleast about 150 MPa; (b)) a modulus of elasticity of at least about 80GPa; and (c) a fracture energy of at least about 2 kN/m.
 29. The shapedarticle of claim 1, wherein the matrix exhibits at least one of thefollowing characteristics: (a) a compressive strength of at least about200 MPa; (b) a modulus of elasticity of at least about 100 GPa; and (c)a fracture energy of at least about 5 kN/m.
 30. The shaped article ofclaim 1, wherein the volume proportion of the reinforcing bodies in thedomain which has the reinforced composite structure is at least about10% and the volume proportion of the reinforcing bodies in any specificdirection of the domain is at least about 5%.